Atrioventricular interactions: a theoretical simulation study.

A quantitative model that describes the complex atrioventricular interactions, based on the structure and myocardial properties of the left atrium (LA) and left ventricle (LV), is presented. The description of the LV follows our earlier study that assumes a nested-shell spheroidal structure with fanlike fiber angle distribution, transmural electrical activation velocity, and the muscle fiber dynamics with the classical passive and active features of the sarcomeres. The LV model is extended here to include an exponential load-dependent relaxation and viscous (strain rate-dependent) features of the LV passive myocardium. The proposed LA model is based on a thin-wall spherical geometry with a random fibrous structure. The atrial muscle features differ from the ventricular muscle by being much stiffer in the passive state and weaker but faster in the active state. The LV and LA compartments are connected to a preload and afterload scheme and interconnected by the mitral flow with its inertial properties. The complex interactions between the LA and the LV are thoroughly studied here, and the calculated results are consistent with well-established experimental data.